06-04-2013, 01:59 AM
I would think that they are mica, they used to put those in the Bakelite blocks too. If in doubt maybe take it out and put it on a resistance-capacitance bridge type tester. As far as I know they used molded micas, installed them in the block, and then potted them with the same tar as the paper caps.
Regards
Arran
Regards
Arran